Oxygen isotope exchange and diffusion in LnBaCo2O6 − δ (Ln = Pr, Sm, Gd) with double perovskite structure

Abstract The interaction of oxygen in the gas phase with double perovskites LnBaCo 2 O 6 − δ (Ln = Pr, Sm, Gd) was studied by the isotope exchange method with gas phase equilibration in the temperature range of 600–850 °C and the oxygen pressure range of 1.3 · 10 − 3 –6.6 · 10 − 2  atm. The oxygen nonstoichiometry of the oxides was determined by means of the thermogravimetric analysis as a function of oxygen partial pressure and temperature in the ranges − 3 ≤ log( Po 2 /atm) ≤ − 0.68 and 600 ≤ T, °C ≤ 850, respectively. The influence of the oxygen nonstoichiometry on the heterogeneous exchange rate and the oxygen tracer diffusion coefficient was discussed. The rate-determining stage of the oxygen surface exchange kinetics for PrBaCo 2 O 6 − δ was found to be different in comparison with SmBaCo 2 O 6 − δ and GdBaCo 2 O 6 − δ . The possible reasons of this observation were considered.